1. Field of the Invention
The present invention relates generally to tube and chamber heat exchangers, and more specifically, to a tube and chamber heat exchanger having main chambers with sub-chambers. The sub-chambers extend outwardly from both planar walls of the main chamber, with the chambers and sub-chambers containing a medium directing insert, which directs the heat exchange medium entering and exiting the main chamber.
2. Discussion of the Related Art
Heat exchangers are commonly utilized in applications where heat is desired to be added or removed. Typical basic heat exchangers are made of generally straight pipes, which channel a heat exchanging medium within, and have a second heat exchange medium flowing on an outer surface of the heat exchanger. Commonly, straight pipes are enhanced with mechanically formed indentations on the outer surface of the straight pipes as well as in some applications on an inner surface of the straight pipes to improve heat exchange performance. Additional plate materials may also be added to the straight pipes' inner surfaces as well as outer surfaces to increase the surface area, which typically improves heat exchanger performance. Headers or manifolds may be attached to each end of the pipes. These headers and manifolds act as receptacles for the heat exchanging medium. Heat exchanging performance of the heat exchanger is limited by the amount of surface area available for the transfer of heat.
To increase surface area to enhance heat exchange performance, typical heat exchangers, such as condensers, incorporate a flat-tube design, usually of extruded tubular material with extended surfaces provided by a corrugated fin material. The corrugated fin material is generally interposed between a pair of extruded tubular materials. This type of a heat exchanger typically includes flattened tubes having a fluid passing therethrough and a plurality of corrugated fins extending between the tubes. The fins are attached to the tubes to increase the surface area of the tubes, thereby enhancing the heat transfer capability of the tubes. A number of tubes and fins may be stacked on top of each other, with a small opening to allow passage of air therethrough. To further improve heat transfer efficiency, the tube's wall thickness may be made thinner. As a result, the parts are lighter in weight, which in turn makes the overall heat exchanger lighter in weight. However, the pressure resistance is reduced, and the thinner tubes are more prone to damage. Also, the assembly process is complicated due to the fragile nature of the parts. In addition, extruded tubes are prone to plugging during the manufacturing process, particularly if a brazing process is utilized. Complexity of the extruding process potentially results in higher costs and higher defect rates. Furthermore, as flat tubes are generally extruded into shape utilizing metal extrusion processes, only material that can be easily extruded into shape is typically made into flat tubes, restricting the material available for flat tubes generally to aluminum and various aluminum alloys.
The overall cost for the flat tube heat exchanging system is higher because a large compressor is necessary to circulate the heat exchanging medium through the small openings of the tubes. Conversely, if a higher powered compressor is not utilized, then additional tubes are necessary to obtain the desired heat exchanging performance, as the smaller tubes reduce flow of the heat exchange medium significantly. The addition of tubes increases the overall cost for the heat exchanging system. Currently, this type of a heat exchanger is used in applications requiring high heat exchanging capabilities, such as automotive air conditioner condensers.
In another tube-and-fin design, the tube can be of a serpentine design, therefore eliminating the need for headers or manifolds, as the tube is bent back and forth in an “S” shape to create a similar effect. Typical applications of this type of a heat exchanger, besides condensers, are evaporators, oil coolers, and heater cores. The serpentine design is essentially a single long tube which transfers the heat exchange medium from the inlet of the serpentine design heat exchanger to the outlet. As a result, the pressure resistance to the heat exchange medium travelling through the heat exchanger is high, which is detrimental to the performance of the heat exchanger. In an application such as an evaporator, wherein pressure drop is unfavorable to the overall performance of a refrigeration cycle, the serpentine design is especially ill suited.
A variation on tube-based heat exchangers involves stacking flat ribbed plates. When stacked upon each other, these ribbed plates create chambers for transferring heat exchanging medium. In essence, this type of a heat exchanger performs in substantially the same manner as tube-and-fin type heat exchangers, but is fabricated differently. This type of a heat exchanger is commonly implemented in contemporary evaporators.
Another variation of a heat exchanger is a tube and chamber design with a medium directing member inserted within the chamber (see, e.g. U.S. Pat. Nos. 7,987,900, 8,393,385, and 8,307,886). The tube and chamber design heat exchanger functions by having a chamber section combined with a medium directing member, wherein heat exchange medium is forced to travel in a turbulent flow. As a heat exchange medium enters the heat exchanger chamber, the heat exchange medium flows in a straight line through a straight tube section. At the end of the straight tube section is a medium directing member which is disposed within the chamber assembly. The medium directing member alters the direction of the heat exchange medium flow from the generally straight line flow to almost a perpendicular flow, while leading the heat exchange medium into the chamber section of the heat exchanger. The chamber section is connected to the tube section, and the chamber section is generally of a larger diameter than the tube section. As the heat exchange medium is introduced into the chamber section, heat exchange medium flows in at least one semi-circular path within the chamber section. As the heat exchange medium completes the semi-circular flow within the chamber section, the heat exchange medium once again comes to contact with the medium directing member. As the heat exchange medium comes to contact with the medium directing member, flow of the heat exchange medium is restored into a generally straight flow in the original flow direction, and the heat exchange medium is led to yet another tube section of the heat exchanger. This process repeats itself within the length of the tube and chamber design heat exchanger.
In a typical tube and chamber heat exchanger assembly, the medium directing member is simply inserted into the chamber assembly. In such an embodiment, the medium directing member does not contribute significantly to the structural rigidity of the heat exchanger, and the chamber assembly and the medium directing member may be coupled together by a limited amount of contact area. In such an embodiment, a suitable application for such a heat exchanger may be restricted to low to moderate internal pressure application usage.
A typical tube and chamber heat exchanger comprises of a plurality of chamber and tube assemblies, with a medium directing member inserted inside each chamber assembly. In this embodiment of a heat exchanger, the manufacturing process may be somewhat complicated as individual medium directing members must be placed within the chamber assembly during an assembly process, without having a locating mechanism to position the medium directing member within the chamber assembly. In such an embodiment, the medium directing member may become dislodged or misaligned during the manufacturing process, thereby decreasing the efficiency of the heat exchanger.